Spatial characterization of ischemia is addressed by evaluating ECG-derived indices: the ST level at J point plus 60 ms, ST_J+60; S wave amplitude, S_a; the upward and downward QRS slopes (I_US and I_DS); and high-frequency QRS in the band 150-250 Hz, HF-QRS_(150-250) over 12-lead ECG signals recorded during prolonged elective PCI. Absolute changes of each index I during coronary occlusion, ¿I, and their relative changes, R_I, were quantified. Mean R S_TJ+60= 14.5, R_Sa= 15.2 and R_IDS= 6.2 times their normal variations in pre-PCI recordings, respectively, showed the most pronounced changes as well as a very similar and distinctive lead-profiles depending on the occlusion site. We conclude that the ECG-derived indices from the final part of the QRS complex show high sensitivity for detection of ischemia. Moreover, their spatial distributions show the largest changes in leads closest to the region adjacent to the occluded artery, which can be considered for occlusion site identification.